This invention relates to an information recording apparatus and method, an information reproduction apparatus and method, an information recording medium, a program storage medium and a program, and more particularly to an information recording apparatus and method, an information reproduction apparatus and method, an information recording medium, a program storage medium and a program which make it possible to appropriately manage security information of AV data recorded on a recording medium.
In recent years, as information recording media of the disk type which can be removably loaded into a recording and reproduction apparatus, various optical disks of different standards such as, for example, a DVD-R (Digital Versatile Disc-Recordable) and a DVD-RW (Digital Versatile Disc-ReWritable) have been proposed. Optical disks of the type just described have a large capacity which can record data of several gigabytes and can record an audio signal and a video signal (AV (Audio Visual) signal) and so forth for long hours.
Incidentally, the MPEG-2 (Motion Picture Experts Group-2) system is an encoding system for digitally compressing an AV signal and is applied where an AV signal is recorded onto a DVD as described above or where a television program signal is recorded onto a hard disk by a hard disk apparatus connected to a receiver.
For example, where an AV signal is recorded onto a predetermined recording medium, a video signal is encoded in accordance with the MPEG-2 system and the resulting coded bit stream is recorded onto the recording medium. Meanwhile, in digital television broadcasting started in recent years, a television program is encoded in accordance with the MPEG-2 system, and the resulting coded bit stream is broadcast in a format called a transport stream. It is possible to record, when a television program is to be recorded, the received transport stream as is onto a recording medium such as a hard disk without decoding or re-encoding the received television program.
Where an AV signal is recorded as digital data on a recording medium in such a manner as described above, since it is possible to copy the AV signal onto another recording medium without deteriorating the same at all, various countermeasures have been proposed and employed in order to solve problems regarding copyright infringement.
For example, in order to control copying of an AV signal, a method is popularly used wherein CCI (Copy Control Information) such as “Copy free” (copying is permitted), “Copy once” (copying is permitted only once), “No more copy” (copying of a further generation is not permitted) and “Copy prohibited” (copying is prohibited) is encoded in the AV signal. More particularly, for example, a DTCP_descriptor prescribed by the DTLA (Digital Transmission Licensing Administrator) is inserted in the AV signal.
In order to suppress uncontrolled copying, a method has been devised of encrypting and recording an AV signal and permitting reproduction of the AV signal only with an apparatus which has a decryption key corresponding to the encryption. For example, in the CPRM (Content Protection for Recordable Media) Specification used for the DVD format, a predetermined field of a pack of an MPEG-2 program stream has the encryption mode of the pack (information representative of whether the pack is encrypted) described therein. For example, where the CPRM Specification is set as “00”, this represents that the pack is not in an encrypted state. On the other hand, where the CPRM Specification is set as “11”, this represents that the pack is in an encrypted state.
Accordingly, in order to reproduce a recorded stream, it is necessary for a conventional reproduction apparatus to acquire the copy control information and the encryption mode as described above. Further, in order to acquire the copy control information and the encryption mode, it is necessary for the reproduction apparatus to analyze the syntax of a bit stream included in the AV stream.
More particularly, for example, in order to acquire DTCP_descriptor as the copy control information, it is necessary to analyze the syntax of a program map table of the transport stream. Further, in order to acquire the encryption mode, it is necessary to analyze the pack header of the program stream.
Incidentally, a method called DTCP is available by which the encryption mode of a stream can be acquired without analyzing the syntax of a program stream. The DTCP has been specified by the DTLA for a protocol (MPEG-TS protocol) for transferring a transport stream through the IEEE1394 digital interface (I/F).
In the DTCP, an EMI (Encrypted Mode Indicator) of 2 bits is transmitted in the header of an isochronous packet used in isochronous transfer of the IEEE1394 interface and thereby represents an encryption mode of the payload of the isochronous packet. For example, where the EMI is “11”, this represents that “Copy prohibited” is set, but where the EMI is “01”, this represents that “No more copy” is set. Further, where the EMI is “10”, this represents that “Copy once” is set, and where the EMI is “00”, this represents that “Copy free” is set.
It is to be noted that, where the DTCP system is used for recording, a method called “Non-cognizant recording mode” is permitted wherein only the EMI is used as copy control information to control copying without analyzing copy control information (Embedded CCI) encoded in the transport stream.
However, the reproduction apparatus as described above has a problem in that reference to the EMI does not allow a distinction between the representation “that the copy control information of the contents is Copy free and the contents are not in an encrypted state” and the representation “that the copy control information of the contents is Copy free and the contents are in an encrypted state”.
Accordingly, although there is a demand to encrypt and record contents onto a recording medium even where the copy control information of the contents is Copy free, it is impossible to encrypt contents whose copy control information is set to Copy free and record the encrypted contents onto a recording medium due to the restriction of the representation only to the EMI described above.